Sense amplifier

ABSTRACT

A sense amplifier for reading a via Read-Only Memory (Via-ROM) is provided. The sense amplifier includes a read circuit, an adaptive keeper circuit and a leakage monitor circuit. The read circuit is connected to the via-ROM. The adaptive keeper circuit is connected to the read circuit. The leakage monitor circuit is connected to the adaptive keeper circuit for forming a current mirror, such that the adaptive keeper circuit compensates a read voltage of a memory cell whose via is opened when a bit-line leakage is happened.

This application is a Continuation Application of U.S. application Ser.No. 15/492,014, filed Apr. 20, 2017, now U.S. Pat. No. 10,181,358, whichclaims the benefit of U.S. provisional application Ser. No. 62/412,881,filed Oct. 26, 2016, the disclosure of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The disclosure relates in general to a sense amplifier, and moreparticularly to a sense amplifier for reading a via Read-Only Memory(Via-ROM).

BACKGROUND

Along with the development of semiconductor technology, various memoriesare invented. Via Read-Only Memory (Via-ROM) records data by vias.Please refer to FIG. 1, which shows an example a Via-ROM 900. Thevia-ROM 900 includes a plurality of word lines WL9, a plurality of bitlines BL9 and a plurality of memory cells, such as code-0 cells C90 andcode-1 cells C91. The source of the code-0 cell C90 is connected to theground, a via at the drain of the code-0 cell C90 is conducted, and theread voltage of the code-0 cell C90 is ground. The source of the code-1cell C91 is connected to the ground, a via at the drain of the code-1cell C91 is opened, and the read voltage of the code-1 cell C91 is high.

The read voltage of one selected code-1 cell C91 may be dropped due tothe bit-line leakages happened on the other code-0 cells C90. If a largenumber of code-0 cells C90 are formed on one bit line, the read voltageof the code-1 cell C91 on this bit line may be greatly dropped andcannot be accurately identified.

Especially, the bit-line leakages are easily happened at high speedvia-ROM or high temperature environment and the read voltage of thecode-1 cell C91 cannot be accurately identified. Therefore, how tocompensate the read voltage under the bit-line leakage is an importantissue nowadays.

SUMMARY

The disclosure is directed to a sense amplifier for reading a viaRead-Only Memory (Via-ROM). An adaptive keeper is used to adaptivelycompensates a read voltage of a memory cell whose via is opened when abit-line leakage is happened.

According to one embodiment, a sense amplifier for reading a viaRead-Only Memory (Via-ROM) is provided. The sense amplifier includes aread circuit, an adaptive keeper circuit and a leakage monitor circuit.The read circuit is connected to the via-ROM. The adaptive keepercircuit is connected to the read circuit. The leakage monitor circuit isconnected to the adaptive keeper circuit for forming a current mirror,such that the adaptive keeper circuit compensates a read voltage of amemory cell whose via is opened when a bit-line leakage is happened.

According to another embodiment, a sense amplifier for reading a viaRead-Only Memory (Via-ROM) is provided. The sense amplifier includes aread circuit, a hybrid keeper circuit and a leakage monitor circuit. Theread circuit is connected to the via-ROM. The hybrid keeper circuit isconnected to the read circuit. The hybrid keeper circuit includes astatic keeper circuit and an adaptive keeper circuit. The static keepercircuit and the adaptive keeper circuit are connected in parallel. Theleakage monitor circuit is connected to the adaptive keeper circuit forforming a current mirror, such that the adaptive keeper circuitcompensates a read voltage of a memory cell whose via is opened when abit-line leakage is happened.

According to alternative another embodiment, a sense amplifier forreading a via Read-Only Memory (Via-ROM) is provided. The senseamplifier includes a read circuit, a static keeper circuit and a leakagemonitor circuit. The read circuit is connected to the via-ROM. Thestatic keeper circuit is connected to the read circuit. The leakagemonitor circuit is connected to the read circuit for forming a currentmirror, such that a read voltage of a memory cell whose via is opened iscompensated when a bit-line leakage is happened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (prior art) shows an example a Via-ROM.

FIG. 2 shows a sense amplifier according one embodiment.

FIG. 3 shows a sense amplifier according another embodiment.

FIG. 4 shows a sense amplifier according another embodiment.

In the following detailed description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

DETAILED DESCRIPTION

Please refer to FIG. 2, which shows a sense amplifier SA1 according oneembodiment. The sense amplifier SA1 is used for reading a via Read-OnlyMemory (Via-ROM) 100. The sense amplifier SA1 includes a read circuitR1, an adaptive keeper circuit AK1 and a leakage monitor circuit LM1.The read circuit R1 is connected to the Via-ROM 100. The adaptive keepercircuit AK1 is connected to the read circuit R1. The leakage monitorcircuit LM1 is connected to the adaptive keeper circuit AK1.

The read circuit R1 is used for reading the read voltage of one memorycell of the Via-ROM 100, such as a code-1 cell C1 whose via is opened,or a code-0 cell (not shown) whose via is conducted. The code-1 cell C1is connected to a word line WL and a bit line BL. Because the via of thecode-1 cell C1 is opened, the read voltage of the code-1 cell C1 shouldbe high. However, when the bit-line leakage is happened, the readvoltage of the code-1 cell C1 may be dropped.

The leakage monitor circuit LM1 is used for providing a leakage currentIoff. The leakage monitor circuit LM1 and the adaptive keeper circuitAK1 are connected to form a current mirror, such that the adaptivekeeper circuit AK1 compensates the read voltage of the code-1 cell C1when the bit-line leakage is happened.

The leakage current Ioff of the leakage monitor circuit LM1 and adriving of the adaptive keeper circuit AK1 have a positive relationship.If the temperature is high or the speed of the Via-ROM is high, thebit-line leakage is easily happened. The leakage current Ioff of theleakage monitor circuit LM1 is high and the driving of the adaptivekeeper circuit AK1 is high. Therefore, even if the read voltage of thecode-1 cell C1 is greatly dropped due to the bit-line leakage, theadaptive keeper circuit AK1 has enough driving ability to compensate theread voltage of the code-1 cell C1.

If the temperature is low or the speed of the Via-ROM 100 is low, thebit-line leakage is not easily happened. The leakage current Ioff of theleakage monitor circuit LM1 is low and the driving of the adaptivekeeper circuit AK1 is low. Therefore, when the read voltage of thecode-1 cell C1 is not dropped or is slightly dropped due to the bit-lineleakage, the adaptive keeper circuit AK1 has low driving ability toslightly compensate the read voltage of the code-1 cell C1.

Further, when a code-0 cell (not shown) is read, the adaptive keepercircuit AK1 has low driving ability or no driving ability, such that theread voltage of the code-0 cell (not shown) can be accurately dropped tobe ground. Thus, even if the bit-line leakages are happened at highspeed via-ROM or high temperature environment and the read voltages ofthe code-1 cell C1 and the code-0 cell (not shown) can be accuratelyidentified respectively.

Referring to FIG. 2, a gate of a transistor T11 of the leakage monitorcircuit LM1 is connected to a gate of a transistor T12 of the adaptivekeeper circuit AK1, and the gate of the transistor T11 is connected tothe source/drain of the transistor T11. A bias voltage Vbias of thetransistor T11 drives the transistor T12 to be turned on.

In this embodiment, the leakage monitor circuit LM1 and the read circuitR1 are substantially the same. The leakage monitor circuit LM1 isconnected to a plurality of dummy cells, such as a plurality of code-0cells C0′. Each gate of the code-0 cells C0′ is connected to a dummyword line WL′ which is grounded. Therefore, the leakage current Ioff canbe simulated.

In one embodiment, the number of the dummy cells may range from 64 to512, such as 64, 128, 511 or 512. The number of dummy cells connected tothe leakage monitor circuit LM1 is programmed.

Please refer to FIG. 3, which show a sense amplifier SA2 according toanother embodiment. In this embodiment, the sense amplifier SA2 includesa read circuit R2, a hybrid keeper circuit HK2 and a leakage monitorcircuit LM2. The read circuit R2 is similar to the read circuit R1, theleakage monitor circuit LM2 is similar to the leakage monitor LM1, andthe similarities are not repeated here. The hybrid keeper circuit HK2 isconnected to the read circuit R2 and includes a static keeper circuitSK2 and an adaptive keeper circuit AK2. The static keeper circuit SK2and the adaptive keeper circuit AK2 are connected in parallel.

In this embodiment, the leakage monitor circuit LM2 and the read circuitR2 are substantially the same. The leakage monitor circuit LM2 isconnected to several dummy cells, such as the code-0 cells C0′. Eachgate of the code-0 cells C0′ is connected to the dummy word line WL′which is grounded. Therefore, the leakage current Ioff can be simulated.

The leakage current Ioff of the leakage monitor circuit LM2 and adriving of the adaptive keeper circuit AK2 have a positive relationship.If the temperature is high or the speed of the Via-ROM is high, thebit-line leakage is easily happened. The leakage current Ioff of theleakage monitor circuit LM2 is high and the driving of the adaptivekeeper circuit AK2 is high. Therefore, even if the read voltage of thecode-1 cell C1 is greatly dropped due to the bit-line leakage, theadaptive keeper circuit AK2 has enough driving ability to compensate theread voltage of the code-1 cell C1.

If the temperature is low or the speed of the Via-ROM 100 is low, thebit-line leakage is not easily happened. The leakage current Ioff of theleakage monitor circuit LM2 is low and the driving of the adaptivekeeper circuit AK2 is turned off. Therefore, when the read voltage ofthe code-1 cell C1 is not dropped, the adaptive keeper circuit AK2 hasno driving ability and will not compensate the read voltage of thecode-1 cell C1.

Further, when a code-0 cell (not shown) is read, the adaptive keepercircuit AK2 has no driving ability, such that the read voltage of thecode-0 cell (not shown) can be accurately dropped to be ground.

In this embodiment, the driving of the static keeper circuit SK2 is lessthan the driving of the adaptive keeper circuit AK2. The static keepercircuit SK2 is used for assisting the adaptive keeper circuit AK2 at thelow temperature.

For example, if the temperature is low, the leakage current Ioff of theleakage monitor circuit LM2 is low and the driving of the adaptivekeeper circuit AK2 is low. Even if the driving of the adaptive keepercircuit AK2 is lowered, the static keeper circuit SK2 still cancompensate the read voltage of the code-1 cell C1. Thus, even if thebit-line leakages are happened at high speed via-ROM or high temperatureenvironment and the read voltages of the code-1 cell C1 and the code-0cell (not shown) can be accurately identified respectively.

In one embodiment, the number of the dummy cells may range from 64 to512, such as 64, 128, 511 or 512. The number of dummy cells connected tothe leakage monitor circuit LM2 is programmed.

Please referring to FIG. 4, which shows a sense amplifier SA3 accordingto another embodiment. The sense amplifier SA3 includes a read circuitR3, a static keeper circuit SK3 and a leakage monitor circuit LM3. Thestatic keeper circuit SK3 is connected to the read circuit R3 tocompensate the read voltage of the code-1 cell C1 when the bit-lineleakage is happened.

Further, in this embodiment, the leakage monitor circuit LM3 isconnected to the read circuit R3 for forming a current mirror. A gate ofa transistor T31 of the leakage monitor circuit LM3 is connected to agate of a transistor T32 of the read circuit R3. When the bit-lineleakage is happened, a bias voltage Vbias of the transistor T31 drivesthe transistor T32 to be turned on, such that a compensation voltage Vcpcan compensate the read voltage of the code-1 cell C1. Thus, even if thebit-line leakages are happened at high speed via-ROM or high temperatureenvironment and the read voltages of the code-1 cell C1 and the code-0cell (not shown) can be accurately identified respectively.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed embodiments.It is intended that the specification and examples be considered asexemplary only, with a true scope of the disclosure being indicated bythe following claims and their equivalents.

What is claimed is:
 1. A sense amplifier, for reading a via Read-OnlyMemory (Via-ROM), comprising: a read circuit connected to the via-ROM;an adaptive keeper circuit connected to the read circuit; a leakagemonitor circuit connected to the adaptive keeper circuit for forming acurrent mirror, such that the adaptive keeper circuit compensates a readvoltage of a memory cell whose via is opened when a bit-line leakage ishappened; wherein the current mirror is formed by a part of the leakagemonitor circuit and a part of the adaptive keeper circuit; and anotherpart of the leakage monitor circuit and the read circuit aresubstantially the same.
 2. The sense amplifier according to claim 1,wherein a leakage current of the leakage monitor circuit and a drivingof the adaptive keeper circuit have a positive relationship.
 3. Thesense amplifier according to claim 1, wherein a gate of a transistor ofthe leakage monitor circuit is connected to a gate of a transistor ofthe adaptive keeper circuit.
 4. The sense amplifier according to claim1, wherein the leakage monitor circuit and the read circuit aresubstantially the same.
 5. The sense amplifier according to claim 1,wherein a number of dummy cells connected to the leakage monitor circuitis programmed.
 6. A sense amplifier, for reading a via Read-Only Memory(Via-ROM), comprising: a read circuit connected to the via-ROM; a hybridkeeper circuit connected to the read circuit, wherein the hybrid keepercircuit includes: a static keeper circuit; and an adaptive keepercircuit, wherein the static keeper circuit and the adaptive keepercircuit are connected in parallel; and a leakage monitor circuitconnected to the adaptive keeper circuit for forming a current mirror,such that the adaptive keeper circuit compensates a read voltage of amemory cell whose via is opened when a bit-line leakage is happened. 7.The sense amplifier according to claim 6, wherein a driving of thestatic keeper circuit is less than a driving of the adaptive keepercircuit.
 8. The sense amplifier according to claim 6, wherein a leakagecurrent of the leakage monitor circuit and a driving of the adaptivekeeper circuit have a positive relationship.
 9. The sense amplifieraccording to claim 6, wherein a gate of a transistor of the leakagemonitor circuit is connected to a gate of a transistor of the adaptivekeeper circuit.
 10. The sense amplifier according to claim 6, whereinthe leakage monitor circuit and the read circuit are substantially thesame.
 11. The sense amplifier according to claim 6, wherein a number ofdummy cells connected to the leakage monitor circuit is programmed. 12.A sense amplifier, for reading a via Read-Only Memory (Via-ROM),comprising: a read circuit connected to the via-ROM; a static keepercircuit connected to the read circuit; a leakage monitor circuitconnected to the read circuit for forming a current mirror, such that aread voltage of a memory cell whose via is opened is compensated when abit-line leakage is happened; wherein the current mirror is formed by apart of the leakage monitor circuit and a part of the read circuit; andanother part of the leakage monitor circuit and another part of the readcircuit are substantially the same.
 13. The sense amplifier according toclaim 12, wherein a gate of a transistor of the leakage monitor circuitis connected to a gate of a transistor of the read circuit.
 14. Thesense amplifier according to claim 12, wherein the leakage monitorcircuit and the read circuit are substantially the same.
 15. The senseamplifier according to claim 12, wherein a number of dummy cellsconnected to the leakage monitor circuit is programmed.